This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Ifa Odu gathers the sixteen principal odu, the Odu Meji, of Ifa divination, the senior tier of a wider system of two hundred and fifty six odu recognised across the Yoruba tradition and its diaspora.
Odu Meji are the sixteen where the opele chain or the counted ikin palm nuts produce the same four marks in both columns; where the two columns differ, the resulting figure belongs instead to the two hundred and forty minor odu. Each figure's mark pattern, recorded in William Bascom's 1969 study of the system, is the exact opposite of one other figure among the sixteen, Eji Ogbe's all single marks opposite Oyeku Meji's all double marks among them. The sequence used here, running Eji Ogbe through Ofun Meji, is the order most widely published from Bascom's and Wande Abimbola's academic work and the one babalawo learn and recite from memory, though Bascom's own fieldwork recorded that the order is not identically fixed among all Yoruba diviners and neighboring peoples, and Yoruba oral tradition separately holds that Ofun, placed last here, was the eldest of the sixteen by descent, so first position reflects arrival rather than seniority.
Each of the sixteen heads its own body of orally transmitted verses, ese Ifa, drawn on by a babalawo or iyanifa when interpreting a cast; the atlas records each figure's mark pattern, position and place in the published sequence, and does not reproduce the verses themselves, which remain the initiated diviner's own transmitted material. A separate sixteen sign system built on counted cowrie shells, the Diloggun tradition, shares several of the same names under different spellings but follows its own count based order.